Medieval Arguments for the Existence of God Part 1: Introduction

This blog is going to pass rather quickly over medieval philosophy (other than this four-part series) for the simple reason that theology is not philosophy. The philosopher A.C. Grayling said it best in his book The History of Philosophy:

“If the starting point for reflection is the acceptance of religious doctrine, then the reflection that follows is theology, or theodicy, or exegesis, or casuistry, or apologetics, or hermeneutics, but it is not philosophy.”

The philosophers of the Middle Ages—while highly intelligent and hugely influential—were largely Christian thinkers that took for granted the truth of scripture as the starting point for reflection. This is an issue because 1) philosophy should take nothing for granted and leave nothing unargued, and 2) if you’re not Christian—and disagree with the very foundation on which medieval philosophy is built—the subject is unlikely to be very insightful or useful to you. (Not to mention that theology especially conflicts with my partiality for fallibilism and critical rationalism.)

And so the interested reader in medieval philosophy will have to look elsewhere for more information on the likes of St. Augustine, St. Thomas Aquinas, John Duns Scotus, William of Ockham, etc. I’m sure there are important philosophical insights to be found in these thinkers, but I have so far been unwilling to commit the time to intensive study.

Nonetheless, there is one topic that has significant philosophical relevance outside of religious dogma, and that is the question of the existence of God, discovered via reason independent of religious revelation. The medieval philosophers—most notably St. Anselm and St. Thomas Aquinas—established the fundamental arguments for God’s existence that are still employed, in one variety or another, today.

It is worth considering these arguments to reflect upon your own beliefs on God, for the purposes of either changing your mind or else strengthening your original convictions. Regardless of where you stand on the issue, it is important that you establish these beliefs yourself—and not rely on others or on the tradition in which you were raised to do the thinking for you.

The four categories of arguments for God’s existence

The medieval philosophers and theologians spent a great deal of time defending the existence of God, establishing the four general approaches people take even today. As you review these arguments, keep in mind that part of what I’m advocating for in this series of posts is that, if one must believe in God, he or she should believe in God for good reasons, and that those reasons should make rational sense.

The four categories of arguments for the existence of God are as follows:

1. Arguments from faith

Arguments from faith, it should be pointed out, are not really arguments at all, but rather assertions or proclamations. God is said to exist because scripture says so, and scripture says so because God exists. This flagrant example of circular reasoning is often covered up under the guise of faith, personal revelation, or the supposed witnessing of miracles. Because arguments for God’s existence are not provided, and the truth of the claims rest solely on appeals to authority and anecdote, we will not consider this line of inquiry in future posts. (Besides, the person with faith has already made up their mind.)

Remember that faith, by definition, is belief in the absence of evidence (otherwise faith wouldn’t be required) that is undisturbed by any possible evidence or arguments. And so, if you adopt the faith position, you should keep a couple of points in mind.

First, reason and evidence are either relevant to the determination of God’s existence or they are not. If you invoke faith, you are committing yourself to the position that belief in God is not a matter of reason or evidence. If reason and evidence does not bear on the issue, it is pointless and disingenuous to provide any reasons or evidence at all, only to resort to faith when you encounter uncomfortable or unanswerable questions.

Imagine that you are at a job interview, and, despite being offered the job, you continue to make your case as to why you would make a great employee. In this situation, whatever else you can say is irrelevant, as you’ve already won the job. Likewise, if you believe that God exists on faith—irrespective of reason—then providing reasons for God’s existence adds nothing to the conversation.

Reason is either relevant or not; if you commit to faith, then say no more. If you commit to reason, then it becomes disingenuous to use faith to avoid contradiction or to support weak arguments.

2. Ontological arguments

Ontological arguments are unique in that they rely almost exclusively on the use of reason with little to no empirical input. They seek to demonstrate the logical necessity of God’s existence. We’ll examine these arguments more closely in part two of this series.

3. Cosmological arguments

Unlike ontological arguments—which seek to prove logical necessity—cosmological arguments seek to demonstrate the existence of God based on the characteristics and structure of the universe as revealed to our senses and to our best science. Cosmological arguments will be discussed in part three of this series.

4. Teleological arguments

Whereas cosmological arguments seek to prove God’s existence through some sort of first cause, teleological arguments point to the necessity of a grand designer as the only legitimate explanation for the apparently deliberate design we see in the natural world. Teleological arguments will be covered in part four of this series.

Preliminary terminology

We will consider the ontological, cosmological, and teleological arguments for the existence of God in parts two, three, and four of this series, so that the reader can decide how persuasive each argument is individually. But before we begin, it is perhaps useful to lay out some terminology to consider as you evaluate each argument and your own particular beliefs:

Theists believe in the existence of God, usually a creator God that intervenes in human affairs and answers prayers.

Deists believe in the existence of God, but reject divine revelation as a source of knowledge. Deists come to believe in God, not through religion, but through reason and the investigation of the natural world. Deists might believe, for example, that God created the universe but does intervene in it, and that organized religion is man-made and not in fact the word of God.

Pantheists believe that the physical universe is identical to God, and that the divine pervades all matter and life. Pantheists do not believe in a personal or anthropomorphic God.

Agnostics believe that the existence of God, the supernatural, or the divine is unknowable. God may or may not exist, but the human mind is incapable of making that determination.

Atheists do not believe that God exists. Atheists either reject the existence of any deities as a positive belief, or, alternatively, use the term only to signal a lack of theism (a—theism), or lack of belief in God, just as one might not believe in the existence of fairies or other mythological creatures. (There’s a sliding scale between atheism and agnosticism depending on how certain you are that there is no God.)

Apatheists are uninterested in the question, and view the subject to be largely irrelevant to everyday matters. (Although, this is more of an attitude than a belief.)

Ignostics believe that the question of God’s existence is meaningless because the word “God” has no coherent definition. Because religious terminology is ambiguous, nothing meaningful can be said about it.

Where do you stand in relation to this spectrum of beliefs? Let’s consider the arguments for God’s existence in more detail—starting with the ontological argument in the next post—while keeping in mind the above distinctions.

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Ryan Boissonneault

Ryan Boissonneault works professionally as a technical writer, holding master’s degrees in both technical writing and business administration. A lifelong learner and an avid reader, Ryan is drawn to the big questions of philosophy, history, and science.
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